It is proposed to pursue the hypothesis that functional effects at the level of the cell membrane, brought about by ethanol, and by lipids that are modified as a result of chronic-ethanol ingestion, may be produced by action at the membrane protein-lipid interface. In the past three years of support several approaches to test the hypothesis have been developed. So far we have found that the adaptation to ethanol-ingestion, consisting of development of a resistance to perturbation by ethanol after chronic-ethanol ingestion-or membrane tolerance, is expressed at the protein-lipid interface. It is now proposed to determine the underlying mechanism and its physical and compositional basis. It is also proposed to pursue results that indicate that ethanol perturbs hydrogen bonding and hydration levels at the protein-lipid interface. We also plan to determine the connection between these effects and altered levels of phospholipid unsaturation that result from the effects of chronic-ethanol ingestion, that preliminary work suggests may important. Many hydrophobic compounds, including ethanol, are classed as general anesthetics and we have found that some more potent compounds were found to interact at the protein-lipid interface, with an apparently higher affinity than would be predicted by hydrophobicity or membrane lipid bilayer partitioning properties. It is postulated that the mechanism is due to an interference with hydrogen bonding. It is therefore proposed to verify this mechanism and to determine if it extends to alcohols and ethanol. The studies will be pursued with natural and model membranes using various fluorescence and other spectroscopic approaches.